What they believed: A band of criminals were stalking the capital, garroting anyone unfortunate enough to come into their path. One unfortunate M.P., Hugh Pilkington, had already fallen victim to them as he made his way home from his club.

Why they believed it: Pilkington was mugged and quite possibly choked - this much is true. But this random incident exploded in the public's imagination. And that was due to magazines and periodicals, who were keen to stoke up a frenzy about the end of transportation to Australia and the activities of ticket-of-leave men (offenders released on a provisional licence), as well as the apparent ineffectiveness of reform programmes for criminals. As a result, in 1863 Parliament passed the Garrotters Act, which reintroduced corporal punishment for armed or violent robbery, and in 1864 the Penal Servitude Act, which made mandatory the police supervision of ticket-of-leave men.

What they believed: In October 1837, a girl called Mary Stevens was walking to Lavender Hill, where she was working as a servant. On her way through Clapham Common, a strange figure leapt at her from a dark alley. He began to kiss her face while ripping her clothes with his claws, before fleeing the scene. The next day, the same figure caused a carriage to crash before breathing fire, laughing and leaping away over a nine foot-high wall. The legend of Spring Heeled Jack was born.

The Times would later report on the Jane Alsop case: on the night of 19 February 1838, she answered the door to a man claiming to be a police officer, who told her to bring a light, claiming "we have caught Spring-Heeled Jack here in the lane". She brought the person a candle, and noticed that he wore a large cloak. She gave him the candle and he tore his cloak off, vomiting blue and white flame from his mouth while his eyes resembled "red balls of fire". He tore at her with his long claws, but she managed to escape him.

For ten years, Spring Heeled Jack gripped the Victorian imagination. He was seen all over the city, an official enquiry was set up, and a man who was believed to be the monster was even put on trial. Many believed it was the alter-ego of a mad Marquess, who had the money to design such a disguise and the time to prank people with it.

Why they believed it: Well now, this is rather a long and complicated story. If you want the full answer, this is easily the best article on it. But basically, it appears to be a classic case of mass hysteria - helped in large part by the occasional prankster, a lot of superstition and of course the burgeoning print media of the day.

What they believed: Such stories appeared in the press as that of a civil servant who saw himself on the other side of Tavistock Square every evening as he walked home from work: 'He tried to give pursuit, but once his double turned a corner he was gone.'

Another woman saw a vision of her sister across Russell Square at the precise moment the woman was dying. Princess Marie Lichtenstein, who occupied the grand Jacobean mansion of Holland House (in Holland Park) wrote a history of the building in which she recorded that 'Whether we respect tradition or not, it is as a received fact, that whenever the mistress of Holland House meets herself, Death is hovering about her.'

Why they believed it: This kind of thing is as old as the hills, of course. But there's an interesting angle: when Britain became the first urbanised society in the world, London became the largest city in the world. A population of one million at the beginning of the century increased to five million by its close. The modest Georgian architecture was replaced by neo-Gothic and neo-classical Victorian public buildings. Hotels, office buildings and blocks of flats in limestone or brick and terracotta rose above the city like giants in the mist.

It's easy to forget the powerful mental effect such a new environment would have had on its denizens. The crowds of people, of a scale never before seen, created a whirlpool of strangers all around. The idea of the death warning wasn't new: there were reports of similar cases as early as the Seventeenth Century. But this was something different; an urban horror that seemed to fit perfectly within the immensity of the growing metropolis.

What they believed: That the sewers of London were full of monstrous pigs that would one day free themselves from their foetid home and run riot through the city.

Why they believed it: It was just your classic urban legend - someone had put it about that a sow had somehow got into the sewer, littered some offspring and fed them on the rubbish being washed into it continually. Chinese whispers ensued, and it was even mentioned in a Daily Telegraph editorial in 1859.

Of course sewers were a major deal for this rapidly expanding city. The Thames was essentially one large open sewer, and cholera was prevalent.

It was only after engineer Joseph Bazalgette constructed miles upon miles of underground brick main sewers to intercept sewage outflows, and 1,100 miles of street sewers, that sewerage stopped flowing freely through the streets and thoroughfares of London.

What they believed: All sorts of things. You could pick any one of hundreds of stories: ghosts, weird cult sightings, the poet Dante Gabriel Rossetti's wife being exhumed and her body being in perfect condition years later, tales of bells attached to graves with string leading under the ground to the coffin in case of premature burial…

Why they believed it: Because massive graveyards were a new thing. Until the city's population exploded, people had simply been buried in church graveyards. But now the city's population had more than doubled, there simply wasn't the space. There were instances of body snatching, of bodies not being buried deeply enough, or of simply being left in the street to rot.

In 1832 Parliament took action, passing a bill that would allow for seven large cemeteries to be built. They'd include Kensal Green, West Norwood, Highgate, Nunhead, Brompton, Abney Park, and Tower Hamlets. The "magnificent seven" particularly appealed to the emerging middle class, keen to distinguish itself from the lower orders.

Why they thought it: Well, you still hear it today, don't you? But what's really interesting is how quickly Victorians saw a business opportunity in a new science.

The first permanent photograph was produced in 1827 and by 1884 film had replaced photographic plates. Spirit photography in America was first used by William H. Mumler in the 1860s. Mumler discovered the technique by accident, after he discovered a second person in a photograph he took of himself, which he found was actually a double exposure. Seeing there was a market for it, Mumler started working as a medium, taking people's pictures and doctoring the negatives to add lost loved ones into them (mostly using other photographs as basis). Mumler's fraud was discovered after he put identifiable living Boston residents in the photos as spirits. By that point plenty of enterprising Londoners were doing much the same.

Another technique involved having the photographer's costumed assistant stealthily stand in the background for a few seconds to create a partially captured, shadowy image. These photographers often worked with spiritualists to create their effects – the culture of séances which had grown out of mesmerism was a huge business.

What they believed: Not so much what they believed, as what interested them. Victorian London might have been preoccupied by the peculiarities of the mind, but was even more concerned about the body. Were those with unusual physical appearances the first steps toward next stage of humanity? Harvey Leach was one of the most famous. Despite his tiny thighs, weak pelvis and foot, and left foot out of proportion to the trunk he was still a professional gymnast – he was regularly seen sitting his horse on his buttocks and standing on his diminutative legs. His legs were so short he could touch the ground with his fingers, yet relied on his legs for demonstrations.

In 1867 The Lancet described the Turtle Woman of Demarara, said to resemble a turtle as a child, she had only six inch long thighs. Miss Marian, Queen of the Amazons, was 8 ft tall when she was 18. In 1882 a special show was written around her at the Alhambra in London, and the entertainment, entitled Babil and Bijou, was a huge success. Miss Marian came on stage wearing a striking costume with pearls and precious stones, and a helmet lifted her height by another 10 inches.

Why they believed it: Two words. Charles Darwin. His 1859 book On the Origin of Species had rocked our world. The obvious question for those who attended these shows was - if that's where we came from, is this where we're going?

What they believed: Animal magnetism was the name given by the German doctor Franz Mesmer in the 18th century to what he believed to be an invisible natural force exerted by animals. He believed that the force could have physical effects, including healing.

John Elliotson, a doctor at University College Hospital, had become a proponent of mesmerism – the curing of various maladies through the laying of hands and 'magnetising' of various metals. His colleague Thomas Wakley thought it all a sham, and set about proving so in a demonstration with Elliotson at his house, then through the medical journal he founded: The Lancet. All the while, mesmerism continued its growth and became more acceptable to the man on the street through cheap lectures and pamphlets.

Why they believed it: The story of Victorian medicine is a journey from superstition to respectability. At the start of the century, the boundaries between quack cures and reputable medicine were hard to define for the average Londoner. By the end of the era much of the medical health system we recognise today had evolved, and while the paranormal healers remained, they occupied a quite different space.

What they believed: This is a classic example from a book called Pith by a Londoner called Newton Crosland:

"In October, 1857, about 1 o'clock in the day, I was going from my office to sign an export bond at the Custom House, Lower Thames Street, a distance of about a quarter of a mile. I was in my usual satisfactory state, of health; my mind was occupied with merely common-place ideas; the traffic in the streets was going on with ordinary monotonous activity, and nothing was apparent there to wake in me the slightest trepidation, when, just as I was crossing Great Tower Street, I was seized with an unaccountable panic. I conceived a dread that I might be attacked by a tiger, and the idea of this horrible fate so haunted me that I absolutely began running in hot haste, and I did not stop until I found myself safe inside the walls of the Custom House. Anything more contemptibly absurd than this apparently causeless fear could scarcely be imagined: a merchant in the streets of London in danger of a wild beast!

The possibility of such a disaster seemed to me to be so ridiculous, the moment I thought about it, that I laughed at myself for allowing so foolish and morbid a fancy to take possession of my mind, and I really considered that I must be fast becoming stupidly nervous. The feeling of apprehension soon, however, passed away, and wonder at my own weakness became predominant. The next morning I took up the Times newspaper, when to my utter astonishment, I read that at precisely the same time when I felt the crazy fear, a tiger had actually escaped from its cage while it was being conveyed from the London Docks, seriously injured two children, and had, to the terror of every observer, ferociously misconducted himself in the public street of Wapping about a mile, as the crow flies, from the spot where I was passing."

The following passage occurs in the Times on Oct. 27, 1857:

"Frightful Occurrence. Yesterday afternoon, about 1 o'clock, as a cattle van was conveying from London Docks a Bengal tiger, the door gave way and the animal bounded into the road, encountered a little boy, sprang upon him, lacerating him in a frightful manner, &c."

Why they believed it: What's interesting is not so much the story, but the wider belief system into which it fits. Newton Crosland was actually a keen defender of Spiritualism - which had begun in the middle of the century in New York. The movement believed that spirits of the dead residing in the spirit world have both the ability and the inclination to communicate with the living: the above story was a symptom of telepathy. It soon began to absorb mesmerists into its ranks. Many famous and renowned people joined - not least Arthur Conan Doyle, the Sherlock Holmes author.

The chatter around telepathy also inspired by fiction, from the clones stalking Dickens' guilty characters to the most famous tale, Jekyll and Hyde, where the outward respectability and inward lust of the character symbolises the hypocrisy of the age. Stevenson's story had its roots in growing uncertainties about the darkness that lay in the subconscious of every Victorian.